This invention relates to a switching element useful in encoders for detecting and measuring rotary or linear displacements, and the velocity and direction of such displacements. An important application of these devices is in monitoring of angular shaft position, direction and speed. Encoders of this type have been known for many years, and they typically generate a train of pulses, one pulse corresponding to a specific small angular or linear displacement, with the pulse rate corresponding to angular or linear velocity.
The pulses are formed by angular or linear movement of one or more contact wipers along and against a switching element having alternating conductive and nonconductive zones. It is important that the transitions between conductive and nonconductive zones be smooth to avoid wiper bounce, and to minimize switching-element and wiper wear for long service life of the encoder.
Known techniques for making such switching elements involve various plating and material-deposition procedures often requiring one or two passes of the elements under construction through a high-temperature oven for material curing and other processes. Each process requires considerable time (typically 30-to-60 minutes) which substantially increases production time and expense. The present invention is a xe2x80x9cno passxe2x80x9d technique which provides a highly satisfactory switching element without lengthy curing time in a high-temperature oven.
The encoder switching element of this invention is characterized by an encoding track formed on a base, the track having alternating conductive and nonconductive segments, the nonconductive segments being a cured solder-mask material. The conductive segments have wiper-contacting surfaces which are preferably gold, and which are in precise alignment and juxtaposition with the nonconductive segments. The invention further includes the process steps of forming a pattern of solder-mask material, and curing the material to define the nonconductive segments.